This invention relates generally to flat panel image display devices and particularly to means for reducing electron back scatter in such devices.
U.S. Pat. No. 4,121,137 issued to Thomas L. Credelle, discloses a system for achieving image brightness uniformity in a flat panel display device. In the Credelle system, the display device is divided into a plurality of channels and electron beams are propagated along the channels. The beam currents of the channels are sensed by a collector and the signals obtained by the sensing are used to adjust the beam currents and to achieve uniformity of image brightness across the viewing area of the display device. The construction and location of the collector do not reduce back scatter of secondary emission electrons and stray electrons at the end of the beam guide meshes, and thus an optimal display may not be achieved in all instances.
Copending application Ser. No. 956,663, filed Nov. 1, 1978 by Frank E. Vaccaro, entitled "Flat Panel Display With Beam Collector" now U.S. Pat. No. 4,216,407 discloses a flat panel display device of the type disclosed in U.S. Pat. No. 4,121,137. In the device disclosed in the copending application Ser. No. 956,663, the ends of the beam guides remote from the cathode are extended. The extended portion of the beam guide nearest the phosphor screen contains no apertures while the extended portion of the beam guide nearest the back panel contains apertures which are substantially larger than the other apertures in the beam guides. A beam collector/pad which is coplanar with the extraction electrodes spans the enlarged apertures. The extended portion of the unapertured beam guide serves as a shield and the beam collector/pad collects electron beams and generates a current which is used to maintain uniform brightness across the display screen.